The present invention relates generally to an apparatus for treating blanks or molded items of plastic material, to put the blanks into various forms.
In treating blanks of plastic material, what is predominantly involved is shaping operations, in the course of which the general configuration of the blank is subjected to change. Such treatment operations may be carried out by means of an apparatus comprising an at least generally cylindrical main frame structure, the longitudinal axis of which extends vertically, and a central cam-bearing drum which is arranged in coaxial relationship with the frame structure and which is mounted rotatably about the longitudinal axis and which is provided on the outside with a plurality of peripherally extending operating cams, and a plurality of treatment stations which are arranged in side-by-side relationship around the periphery of the frame structure, the treatment stations having tools which are operable to carry out processing or treatment operations on the plastic blanks. The tools may be carried by vertically movable tool carriages, each of which can be moved up and down by a cam roller which is guided by means of a cam on the rotatable drum.
When reference is made hereinbefore and also hereinafter in this specification to the main frame structure being of generally cylindrical configuration, that is intended to mean that the frame structure is of a peripheral configuration. While therefore it may be at least substantially cylindrical in the strict sense, it may also be in the form of a polygonal cross-section or in the form of a hollow cylinder with flat portions at the peripheral surface thereof.
When using such an apparatus for carrying out operations for changing the shape of a plastic blank, it may be necessary to apply considerable forces which have to be transmitted to the tools from the cams on the cam drum. As the treatment stations with the operating tools are mounted on the main frame structure on the outside thereof, they will normally project outwardly therefrom so that there is a generally radial spacing between the cam drum which is arranged within the frame structure and the vertical plane or axis in which the tools are moved to produce the shaping effect on the blank. Now, it will be seen that the above-mentioned forces required for shaping the blank have to be transmitted across the radial spacing mentioned above, with the result that the forces occurring in the shaping operation give rise to the generation of moments, the magnitude of which also increases with an increasing spacing between the cam drum and the point at which the forces act on the respective tool carriage. In that connection, account is to be taken of the fact that it is not possible for the spacing between the cam drum or the cam follower rollers which are guided thereby, and the associated tool, to fall below a certain minimum value as the arrangement must include guides for the holders carrying the tool which must therefore be disposed in the above-mentioned spacing, while in addition, in order to provide for a certain degree of ease of monitoring and gaining access to the tools and other associated components, they must be displaced somewhat outwardly relative to the housing frame structure of the apparatus.